LESSON 5 Flashcards
A multicellular organism needs to coordinate _____ across different tissues & organs
cell division
critical for normal growth,
development & maintenance
cell division
not all cells can have the same ____
cell cycle
____ of cell division varies by cell type
Frequency
embryo
- cell cycle < ______
20 minute
skin cells
- divide frequently throughout life ________cycle
12-24 hours
liver cells
- retain ability to divide, but keep it in reserve divide once every _________
year or two
cell cycle 20mins
embryo
12-24 hrs cycle
skin cell
divides only once or twice a year
liver cells
do not divide at all after maturity permanently in G0
Two irreversible points in cell cycle
- replication of genetic material
- separation of sister chromatids
- process is assessed & possibly halted
Checkpoints
cell cycle controlled by STOP & GO chemical signals at critical points
checkpoints
signals indicate if key cellular
processes have been completed correctly
checkpoints
3 major checkpoint
G1/s, g2/m, spindle fiber scheckpoint
can DNA synthesis begin?
`g1/s checkpoint
has DNA synthesis been completed correctly?
g2/m checkpoint
commitment to mitosis
g2/m checkpoint
are all chromosomes attached to spindle?
spindle checkpoint
can sister chromatids separate correctly?
spindle checkpoint
primary decision point
- “restriction point”
g1/s checkpoint
if cell receives “GO” signal, it _____
divides
internal signals: ______, ______
cell growth (size), cell nutrition
external signals: “____-______”
growth factors
if cell does not receives signal, it exits cycle & switches to _______________
G0 phase
non-dividing, working state
g0 phase
non-dividing, differentiated state
g0 phase
in G0, but can be “called back” to cell cycle by external cues
liver cells
highly specialized
- arrested in G0 & can never divide
nervous & muscle cells
chemical signals in cytoplasm give cue
activation of cell division
signals usually mean proteins
activators , inhibitors
internal signals
- “__________”
external signals
- “_________”
promoting factors
growth factors
protein that regulate the metabolism, proliferation, apoptosis, subcellular trafficking, inflammation and other important physiological process.
phosporylation
primary mechanism control
phosporylation
kinase enzymes
- either activates or inactivates cell signals
checkpoints who
Leland H Hartwhell
Cdks who
Tim Hunt
cyclins who
Sir Paul Nurse
Growth factors
Nutritional state of cell
Size of cell
Cdk/G1 cyclin
Replication completed
DNA integrity
Cdk/G2 Cyclin (MPF)
MPF
Mitosis Promoting Factor
Chromosomes attached at metaphase plate
APC (spindle scheckpoint)
APC
Anaphase Promoting Complex
normal growth factor genes that become oncogenes (cancer-causing) when mutated
proto-oncogenes
stimulates cell growth
proto-oncogenes
if switched “ON” can cause cancer
proto-oncogenes
- example: RAS (activates cyclins)
proto-oncogenes
inhibits cell division
tumor-supressor genes
if switched “OFF” can cause cancer
tumor-suppressor genes
example: p53
tumor suppressor genes
_____ is essentially a failure of cell division control
Cancer
unrestrained, uncontrolled cell growth
cancer
gene ___ plays a key role in G1/S restriction point
p53
____ protein halts cell division if it detects damaged DNA
p53
ALL cancers have to shut down _____ activity
p53
____ is the Cell Cycle Enforcer
p53`
p53 discovered at Stony Brook by _________
Dr. Arnold Levine
6 KEY MUTATION HITS
unlimited growth
ignore checkpoints
escape apoptosis
immortality which means unlimited divisions
promotes blood vessel growth
overcome anchor & density dependence
- turn on growth promoter genes
unlimited growth hit
- turn off tumor suppressor genes (p53)
ignore checkpoints hit
- turn off suicide genes
escape apoptosis hit
turn on chromosome maintenance genes
immortality hit
turn on blood vessel growth genes
promote blood b=vessel growth hit
turn off touch-sensor gene
overcome anchor & density dependence
What causes these “hits”?
UV radiation
chemical exposure
radiation exposure
heat
cigarette smoke
pollution
age
genetics
abnormal cells remain at original site as a lump
benign tumor
p53 has halted cell divisions
benign tumor
most do not cause serious problems &
can be removed by surgery
benign tumor
cells leave original site
malignant tumor
lose attachment to nearby cells
- carried by blood & lymph system to other tissues
malignant tumor
start more tumors
malignant tumor
start more tumors
metastasis
impair functions of organs throughout body
malignant tumors
- kills rapidly dividing cells
high-energy radiation
stop DNA replication
- stop mitosis & cytokinesis
- stop blood vessel growth
chemotherapy
